This invention relates to a stable lithium diisopropylamide (LDA) composition, and a method of its preparation.
Lithium diisopropylamide (LDA) is widely used as a reagent in the preparation of pharmaceuticals and specialty chemicals. LDA has a low solubility and irreversibly precipitates in hydrocarbon solvents. Consequently, LDA is not commercially available in solution form. The only commercially available LDA has been as a pyrophoric solid or slurry in hydrocarbon, and this has been available only in low volumes. The safety hazard in the shipment and handling of the pyrophoric LDA solid or slurry, as well as the difficulty in using these forms of LDA in reactions, severely limit the usefulness of these LDA forms in commercial applications.
Users of LDA generally prefer an LDA solution. Although LDA is soluble in ethers, it is quite unstable in this medium and quickly decomposes at room temperatures. Therefore, large volume users of LDA must synthesize their own LDA as it is needed, typically by reacting n-butyllithium with diisopropylamide in cold tetrahydrofuran (THF). This reaction is fairly easy to carry out, but may present safety hazards for those users unfamiliar in the handling of pyrophoric n-butyllithium.
Accordingly, the need exists for a stable and nonpyrophoric form of lithium diisopropylamide which could be produced and shipped in quantity and which presents fewer handling problems than the currently available forms of lithium diisopropylamide.